Bridge section shifting drive for a bridge laying apparatus

ABSTRACT

A bridge laying apparatus for longitudinally displacing a bridge section includes a pinion shaft; a pinion secured to the pinion shaft for moving with the pinion shaft as a unit; a bearing rotatably and axially slidably supporting the pinion shaft; and a hydraulic power cylinder unit. The power cylinder unit includes a cylinder coaxially surrounding the pinion shaft and defining a cylinder chamber; and a hollow piston axially slidably accommodated in the cylinder chamber and being axially driven by a pressure prevailing in the cylinder chamber. The hollow piston surrounds the pinion shaft. There is further provided a coupling arrangement connecting the hollow piston with the pinion shaft for axially displacing the pinion shaft and the pinion into an axially advanced and into an axially withdrawn position. In the axially advanced position the pinion is situated in a region where it is adapted to mesh with a rack of a bridge section and in the axially withdrawn position the pinion is situated at a clearance from such region.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the priority of German Application No. P 44 01768.5 filed Jan. 24, 1994, which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

This invention relates to a driving device incorporated in a bridgelaying apparatus and is of the type which has on either side a pinionwhich is designed to mesh with a rack mounted longitudinally along abridge section to advance the bridge section as the pinion is rotated.Each pinion may be moved axially by a hydraulic power cylinder unit intoand out of the zone of the rack.

In published International Application WO 90/05216 a bridge layingvehicle is disclosed which has a laying arm designated as a layingdevice and a receiving device associated with the laying device. Thelaying arm as well as the receiving device are provided with a drivingdevice which is adapted to shift individual bridge sections or aplurality of interconnected bridge sections on the laying-arm and/or thereceiving device. The driving devices have on either side rack-drivingpinions which mesh with racks which, as a rule, are arranged along theguide rails at the lower chord of the bridge sections.

In handling bridge sections the driving devices provided with therack-driving pinions must perform three functions:

they have to drive at least one bridge section in the longitudinaldirection;

they have to immobilize at least one bridge section on the layingapparatus; and

they have to be releasable from all bridge sections to make possible afeed of interconnected bridge sections by the respective other drive orto make possible a lowering of a bridge section past the driving devicewithout a collision between the rack of the bridge section and thepinion of the driving device.

For releasing the connection between the drive and the rack of therespective bridge section, German Offenlegungsschrift (applicationpublished without examination) 35 17 724 discloses an axiallydisplaceably supported driving pinion intended to mesh with the rack,and the axial position of the pinion may be changed by a hydrauliccylinder arranged offset relative to the rotary axis. It is adisadvantage of such a solution that because of the eccentricarrangement of the hydraulic cylinder stresses and misalignments withinthe pinion guide box may occur and, as a result, the various functionsmay be adversely affected to a substantial extent.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a driving device of theabove-outlined type which makes possible a stress-free displacement ofthe rack-driving pinion.

This object and others to become apparent as the specificationprogresses, are accomplished by the invention, according to which,briefly stated, the bridge laying apparatus for longitudinallydisplacing a bridge section includes a pinion shaft; a pinion secured tothe pinion shaft for moving with the pinion shaft as a unit; a bearingrotatably and axially slidably supporting the pinion shaft; and ahydraulic power cylinder unit. The power cylinder unit includes acylinder coaxially surrounding the pinion shaft and defining a cylinderchamber; and a hollow piston axially slidably accommodated in thecylinder chamber and being axially driven by a pressure prevailing inthe cylinder chamber. The hollow piston surrounds the pinion shaft.There is further provided a coupling arrangement connecting the hollowpiston with the pinion shaft for axially displacing the pinion shaft andthe pinion into an axially advanced and into an axially withdrawnposition. In the axially advanced position the pinion is situated in aregion where it is adapted to mesh with a rack of a bridge section andin the axially withdrawn position the pinion is situated at a clearancefrom such region.

According to an advantageous feature of the invention, the cylinderhousing of the hydraulic power cylinder unit (piston/cylinder unit) issituated externally, about the bearing housing in which the rack-drivingpinion is supported. The axially effective form-fitting and/orfrictional connection between the piston/cylinder unit and the pinion ismade as a flange connection of the free end of the hollow piston rod ofthe piston/cylinder unit and a bearing sleeve which is axially guided inthe bearing housing and which supports the shaft of the pinion. Formonitoring and controlling the horizontal or axial displacements of thepinion, two proximity switches responding to the end positions of thepinion are provided. The limit switches cooperate with an element, suchas a pin, extending outwardly from the free end of the hollow pistonrod.

To make possible an evaluation and control of the pinion-causeddisplacement of the bridge section on the laying device, the pinionshaft is connected with an angular position sensor whose signals, asdetermined by the structural features, may represent the displacementpath of the bridge sections. According to a preferred embodiment of theinvention, the pinion shaft is provided with outer teeth which areconnected with the measuring shaft of the rotary position sensor bymeans of an intermediate gear.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic side elevational view of a bridge laying vehiclecarrying a bridge laying apparatus which incorporates the invention andon which two bridge sections are position.

FIG. 2 is a side elevational view of the bridge laying apparatusincorporating the invention.

FIG. 3 is an enlarged detailed sectional view taken along line III--IIIof FIG. 2.

FIG. 4is an enlarged sectional front elevational view of a component ofFIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The vehicle 1 illustrated in FIG. 1 is provided with a bridge laying orlaunching apparatus 2 which is essentially formed of a shifter frame 3and a laying arm 4 articulated thereto. The laying arm 4 as well as theshifter frame 3 are each provided with a respective driving device 5 and6 for the bridge sections B1 and B2. Also referring to FIG. 2, thedrives 5 and 6 are of identical construction; each has a hydro-motor 7,a gearing 8 and a hydraulically operable brake 9 arranged therebetween.

Also referring to FIG. 3, the gearing 8 is secured to the carrierstructure 11 of the laying arm 4 by fittings 10. The gearing 8 is aT-shaped angular gearing and has on either side of its central plane 12a driving hub 13 provided with a spline bore. It is noted that FIG. 3shows only one side (that is, to the left of the center plane 12) of anotherwise substantially symmetrical construction.

The carrier structure 11 has on both sides a support housing or guidetube 14 provided on its inner face with a guide sleeve (or slide sleeve)15. In the housing 14 a bearing sleeve 16 is supported which on itsouter face has longitudinal, axially extending grooves 17 into whichproject radially inwardly oriented pins 18 secured to the supporthousing 14. The pins 18 ensure that the bearing sleeve 16 is preventedfrom rotating during its axial displacement. Inside the bearing sleeve16 a hollow pinion shaft 21 is supported by a radial bearing 19 and aradial/axial bearing 20. To the outer end of the pinion shaft 21 a rackdriving pinion 22 (hereafter only briefly referred to as pinion) issecured. The pinion 22 is to be brought into and out of a meshingengagement with rack pins 23--only one is visible in FIG. 3--of a rackmounted along the guide rails 24 of the bridge sections B1, B2. Thebearing sleeve 16 has a flange 25 at its outer end, adjacent the pinion22.

Also referring to FIG. 4, a hydraulic power cylinder unit(piston/cylinder unit) 26 surrounds the support housing 14; the unit 16has a cylinder 27 which is fixedly bolted to the respective carrierconstruction 11. Within the annular cylinder chamber 28 of the cylinder27 a hollow, annular piston 29 is slidably guided by means of a hollow,cylindrical, tubular piston rod 30. The cylinder 27 has at the axialends of the cylinder chamber 28 inlets 31 and 32 for the intake andoutlet of a pressure medium. At its outer end the hollow piston rod 30has a radially inwardly oriented flange 33 whose inner diameter is lessthan the outer diameter of the flange 25 of the bearing sleeve 16, sothat the piston rod 30 presses the bearing sleeve 16 and thus the pinion22 in the direction of the pins 23 of the rack upon outward movement ofthe piston 29 (which is effected by introducing pressurized hydraulicmedium at inlet 32behind the piston 29).

Reverting to FIG. 3, to that end of the piston rod 30 which is remotefrom the piston 29 a ring 34is secured which is cross-sectionallyreduced in the region of the rack pins 23. The inner diameter of thering 34is less than the outer diameter of the flange 25 of the bearingsleeve 16, so that the piston rod 30, upon retraction of the piston 29carries with it the bearing sleeve 16 and thus the pinion 22 from theregion of the rack pins 23.

A radially projecting actuator bar 35 is threaded into the ring 34 in aregion thereof which is remote from the rack pins 23. In both terminalpositions of the free end of the actuator bar 35 respective proximityswitches 36 and 37 are arranged which operate as limit switches and withthe aid of which an unequivocal indication of the respective endpositions of the pinion 22 and thus a state of engagement of the pinion22 with the rack pins 23 or a state of disengagement of the pinion 22from the pins 23 may be securely determined.

A drive shaft 38 is accommodated inside the hollow pinion shaft 21 andextends coaxially therewith. The drive shaft 38 is torque-transmittinglycoupled to the pinion 22 by means of a splined shaft/splined hubconnection 39. At its other end the drive shaft 38 istorque-transmittingly connected with the respective drive hub 13 of thegearing 8 by means of a further splined shaft/splined hub connection 40.

That end of the hollow pinion shaft 21 which is remote from the pinion22 is provided with outer teeth 41. An intermediate toothed gear42supported by the carrier structure 11 connects the outer teeth 41 withthe pinion 43 supported on the measuring shaft of an angular positionindicator 44 mounted on the carrier structure 11. In this manner, inaddition to the axial end positions of the pinion 22 sensed by the limitswitches 36, 37, the number of revolutions of the pinion 22, and thusthe displacement path of the bridge sections B1 and B2, effected by therotation of the pinion 22, may be determined.

It will be understood that the above description of the presentinvention is susceptible to various modifications, changes andadaptations, and the same are intended to be comprehended within themeaning and range of equivalents of the appended claims.

What is claimed is:
 1. A bridge laying apparatus for longitudinallydisplacing a bridge section having a longitudinally extending rack; theapparatus comprising(a) a pinion shaft; (b) a pinion secured to thepinion shaft for moving with said pinion shaft as a unit; (c) bearingmeans for rotatably and axially slidably supporting said pinion shaft;(d) a hydraulic power cylinder unit including(1) a cylinder coaxiallysurrounding said pinion shaft and defining a cylinder chamber; (2) meansfor pressurizing and depressurizing said cylinder chamber; and (3) ahollow piston axially slidably accommodated in said cylinder chamber andbeing axially driven by a pressure prevailing in said cylinder chamber;(e) coupling means connecting said hollow piston with said pinion shaftfor axially displacing said pinion shaft and said pinion into an axiallyadvanced and into an axially withdrawn position; in said axiallyadvanced position said pinion is situated in a region where it isadapted to mesh with a rack of a bridge section and in said axiallywithdrawn position said pinion is situated at a clearance from saidregion.
 2. The bridge laying apparatus as defined in claim 1, whereinsaid bearing means includes a housing;said hydraulic power cylinder unitbeing disposed about said housing.
 3. The bridge laying apparatus asdefined in claim 2, wherein said hydraulic power cylinder unit includesa hollow piston rod affixed to said hollow piston in axial alignmenttherewith; further wherein said bearing means comprises a bearing sleevecoaxially surrounding said pinion shaft and axially slidably guided inand by said housing; said bearing sleeve relatively rotatably supportingsaid pinion shaft and being secured to said hollow piston rod foraxially moving therewith as a unit; and said coupling means includingmeans for axially force-transmittingly connecting said bearing sleevewith said pinion shaft.
 4. The bridge laying apparatus as defined inclaim 3, further comprising first and second stationarily supportedproximity switches spaced parallel with a direction of axialdisplacement of said pinion shaft;and an actuator member affixed to saidhollow piston rod for cooperating with said proximity switches such thatthe first proximity switch responds when said pinion shaft attains saidadvanced position and the second proximity switch responds when saidpinion shaft attains said withdrawn position.
 5. The bridge layingapparatus as defined in claim 1, further comprising an angulardisplacement indicating means for responding to and emitting a signalrepresentative of, an angular position of said pinion shaft.
 6. Thebridge laying apparatus as defined in claim 5, wherein said angulardisplacement indicating means includes a toothed gear and said pinionshaft includes circumferentially arranged external teeth; furthercomprising an intermediate toothed gear meshing with said external teethand said toothed gear of said angular displacement indicating means.